The present invention relates to a rod-like element for application in spinal or trauma surgery, and a stabilization device using such a rod-like element.
European Patent EP 0 669 109 B1 describes a stabilization device for stabilizing neighboring thoracic vertebrae. The device comprises two pedicle screws and a strap that is fixed in the receiving part of the pedicle screws by a clamping screw. The device contains a support element in the form of a pressure-resistant support body that is mounted on the strap. This stabilization device is not torsion-resistant. Furthermore, the flexural elasticity and the tensile and compression force elasticity are coupled.
U.S. Patent Published Application 2003/0109 880 A1 describes a dynamic stabilization device for vertebrae. The device comprises a first and a second screw to be anchored in the vertebra, each of which has a receiving part for the insertion of a spring connecting the screws, and such a spring. The spring, a helical spring with closely neighboring turns, similar to a helical tension spring, is fixed in the receiving parts by means of clamping screws. This, however, poses the risk that the spring, due to its flexibility, escapes the pressure of the clamping screw, thus causing the connection between the spring and the bone screw to loosen. Moreover, the flexural elasticity and the elasticity with respect to tensile and compression forces are coupled in this device.
German Patent Application DE 102 36 691 A1 describes a dynamic stabilization device for bones, in particular for vertebrae. This device comprises at least two bone anchoring elements and a rigid rod connecting the bone anchoring elements. A spring element is provided on the rod and arranged between the bone anchoring elements. One of the bone anchoring elements is connected to the rod so that it is capable of shifting in the direction of the rod axis, whereby the rod includes a stop for limiting the motion of the anchoring element that is capable of shifting. This stabilization device allows for a translational motion in the direction of the rod axis. In addition, the one anchoring element is capable of shifting relative to the rod and therefore providing for rotational motion of the anchoring element around the rod axis, but not for lateral flexion of the rod.
Therefore, there is a need for dynamic control of motion for the dynamic stabilization of pre-damaged intervertebral disks as well as artificial vertebral disks, in particular those with no inherent mechanism for limiting mobility. Particularly suited for this purpose are stabilization devices with an elastic element, such as the ones described above, which are inserted from the posterior side of the spine.
It is therefore an object of the invention to provide a rod-shaped element for application in spinal or trauma surgery and a stabilization device with such a rod-shaped element which is suited for dynamic posterior stabilization or for dynamic guidance of motion in the presence of a pre-damaged intervertebral disk or in the use of artificial intervertebral disks, in which various degrees of freedom can be adjusted independently of each other.